Precision multiplier



lDlsP- OF SHAFT I3 AT TEEMINALs FREDERICK Ml. CUNNINGHAM RICHARD a.MINCE QUENTIN J. EVANS INVENTORS.

BY fiz ATTORNEY.

F. W. CUNNINGHAM ETAL PRECISION MULTIPLIER Filed Jan. 7, 1953 Aug. 7,1962 m B m T a F 4 s w m w e M S a R m & w m D 0 C /s A A A2 025556 2 0uu fio k. a z m u 9 T o 3 F 0 u A e a m J H M V M S w 4 I 0 w z 3 0 a SH M. S w m m m fi o q B 9 M m I 0 Am. 0252.? A 4 uwu5 1 AT TERMINALS 22bUnited States Patent PRECISION MULTIPLIER Frederick W. Cunningham,Stamford, (loan, and Richard Y. Miner, Port Washington, and Quentin J.Evans, Long Island City, N.Y., assignors to American Bosch ArmaCorporation, a corporation of New York Filed Jan. 7, 1953, Ser. No.329,944- Claims. (ill. 32.34.3.5)

This invention relates to computers and has particular reference toprecision multipliers having electrical and mechanical inputs and anelectrical output.

The accuracy requirements of present day analog cornputers demandsextreme precision not available in prior multipliers. Prior devices ofthis type have included wound resistance voltage dividers orauto-transformers in which the output volt-age is proportional to theproduct of the excitation voltage and the displacement of the movablecontact, but in these devices the output varies in finite steps as thecontactor moves from turn to turn on the winding. An inductionpotentiometer, on the other hand, produces a smoothly varying voltageproportional to the product of the excitation voltage and the rotordisplacement but is not universally applicable since the linear outputis available over little more than 90 of rotor displacement.

In a preferred embodiment, the present invention uses the mechanicalinput to drive the movable contacts of a pair of selector switches, andto simultaneously drive a pair of induction potentiometer rotorwindings. The ratio of speeds is such that for each half revolution ofthe induction potentiometer rotor the movable contacts travel from onelive contact to the selector switch to a similar position on the nextadjacent live contact.

Alternate stationary contacts of one selector switch are connected toequally spaced taps on a winding which is energized by the electricalinput, and alternate stationary contacts of the other selector switchare connected to taps intermediate of the first taps on the sameenergized winding. The primary winding of the induction potentiometer isenergized by the electrical input. The output of one selector switch isconnected in series one induction potentiometer output while the outputof the other selector switch is connected in series with the otherinduction potentiometer output. Each selector switch provides a voltagewhich increases in steps as the mechanical input increases while theinduction potentiometer acts to interpolate to either side of the stepto provide a voltage accurately proportional to the displacement of theinput shaft (for constant electrical input) over recurring limits ofrotation of about 100 for each half revolution of the potentiometerrotor.

The output of the combination of one selector switch and inductionpotentiometer winding leads the output of the combination of the otherselector switch and in duction potentiometer winding by 90 ofpotentiometer rotor displacement. A make-before-break relay is actuatedby the mechanical input to select the output of the proper combinationto provide a continuous output which is accurately proportional to theproduct of the inputs over the complete range of mechanical input.

For a more complete understanding of the invention, reference may be hadto the accompanying diagrams in which:

FIG. 1 is a schematic electrical wiring diagram of the invention;

FIG. 2 is a curve of the output of one induction potentiometer windingvs. rotor displacement;

FIG. 3 is a curve of the output of the other induction potentiometerwinding vs. rotor displacement;

FIG. 4 is a series of curves showing the outputs of "ice one selectorswitch, reversing switch and their total output vs. potentiometer rotordisplacement;

PEG. 5 is a series of curves showing the outputs the other selectorswitch, reversing switch and their total output vs. potentiometer rotordisplacement; and

PEG. 6 is a curve showing the output of the present device vs.potentiometer rotor displacement.

Referring now to FIGURE 1, shaft 10 of a computer is driven by means ofgearing 11 by the crank 12 which also drives shaft 13. The value Xrepresented by the angular displacement of shaft 10 may be read on dial14.

The other multiplier Y is represented by an alternating voltageproportional in magnitude to Y which is applied to the input terminals18'. For the purposes of this description the voltage at terminals 13'will be assumed to be constant and equal to unity so that the output ofthe multiplier, XY, can be described as being proportional to X. Thisproduct XY is obtained at terminals -14 and may be read on the scale ofvoltmeter V which is connected across terminals 14, for example, or maybe used as the input to other computing circuits.

Shaft 13 drives the rotor of an induction potentiometer l7 and displacesthe rotor windings 15 and 16 relatively to the stator winding 18. Aninduction potentiometer is essentially a transformer in which asecondary winding is adapted to be displaced angularly in the field ofthe primary winding and which is constructed in a manner such that theoutput voltage of the secondary winding is proportional to the angulardisplacement of the secondary winding from its position of null voltage(perpendicular to the primary winding) for constant primary excitation.The linear relationship between the displacement and the output voltageis effective for angular values of approximately 50 to either side ofthe two zero or null positions.

FIGURE 2 which is a curve of the output of winding 15 versusdisplacement of the shaft 13 for constant excitation at terminals 18shows that the output voltage of rotor winding 15 is linearlyproportional to the angular displacement of shaft 13 from the zeroposition (i.e. where the magnetic axis of winding 15 is perpendicular tothe magnetic axis of winding '18) between approximately 50 and +50".Also, the output voltage of rotor winding 15 is negatively proportionalto the angular displacement of shaft 13 from the 180 position betweenvalues of li50, i.e. from 130 to 230. Between values of 50 and 130 andbetween 230 and 310 the output voltage of winding 15 does not maintain alinear relationship to the displacement of the shaft 13.

For the purposes of this invention, a second rotor winding 16,perpendicular to the first rotor winding 15, is wound on the rotor ofinduction potentiometer 17. The output voltage of rotor winding 16 isthen proportional to the angular displacement of shaft 13 for 50 oneither side of the position of shaft 13 and is negatively proportionalto the angular displacement of shaft 13 from its 270 position betweenthe limits of 270:50". The curve of output voltage of rotor winding 16versus the displacement of shaft 13 is shown in FIG. 3. In analternative arrangement, two conventional induction potenti-ometershaving one secondary winding each may be used instead of the singleinduction potentiometer 17 which has two mutually perpendicularsecondary windings l5 and 16.

Shaft 13 also drives the cams 19 and 20 to operate the reversingswitches 22 and 23 by means of the cam followers 25 and 27 which areurged against the cam surfaces by the respective springs as and Rotorwinding 15 is connected to the movable contacts 22a of reversing switch22. The output of switch 22, taken at terminals 22b is plotted againstthe rotational displacement of shaft 13 in FIG. 4 and is seen toapproximate a saw tooth wave with flattened peaks. Similarly, rotorwinding 116 is connected to the movable contacts 23a of switch 23 sothat the output of switch 23*, taken at terminals 23b, plotted againstthe rotational displacement of shaft 1 approximates a saw toothed wavewith flattened peaks, as seen in FIG. 5. The output of rotor winding 16lags the output of rotor winding by 90 of displacement of shaft 13. Itwill be noted that the cams 19 an 20 cause reversal of the outputs ofrotor windings 15 and 16 in the non-linear intervals, i.e. near 90 and270 for winding 15 and near 0 and 180 for winding 10.

Shaft drives the movable contacts 29 and 30 of the multiple selectorswitches 31 and 32 respectively. Alternate stationary contacts 31a, 31c,31a of switch are connected respectively to the equally spaced alternatetaps 33, 35, 37 of auto transformer winding tap is the end tap of thewinding 4-0. The alternate stationary contact 32b, 32d, 32 of switch 32are connected to the alternate taps 34, 36, .38 on transformer winding4-0, said taps being located midway between the taps 33 an 35, 35 and37, 37 and 39. Contacts 3115, 331d, 31 320, 32c and 32@ of the switches31 and 52 are electrically dead.

The winding 40 is energized by the voltage at terminals 10', and thevoltage between any two adjacent taps is designated as 2E. Thus, asshaft 10 drives the movable contact 23 in a direction corresponding toincreasing X, the output voltage of switch 31, shown by the dotted curvein FIG. 4, increases by steps of 4E, there being a period of zerovoltage between steps as the movable contact 23 rides over a deadstationary contact 31b, 31d, 31 Similarly, the movable contact 30 ofswitch 32 is driven about its stationary contacts to produce an outputvoltage as shown by the dotted curve in FIG. 5, where the voltageincreases by steps of 413 after the first step of 2E, and where theaction of switch 32 leads the action of switch 31 by 90 of displacementof shaft 13.

Movable contact 29 is connected to one of terminals 22b, while the otherterminal 22b is connected to terminal 4-1 of relay 42, so that thevoltage between terminal 41 and the common lead 4-3, which is connectedto end tap 33, is the algebraic sum of the voltage outputs of switches31 and 22. This voltage may be represented by the solid curve of HG. 4.

it will be seen that the voltage between terminal 41 and lead 43 varieswith respect to the displacement of shaft 3 in the following manner:Between 0 and degrees the voltage is proportional to the shaftdisplacement; at 50 the movable contact 29 is disconnected from contact31a to interrupt the circuit and the voltage drops to zero; the voltageremains zero between 50 and 130 while contact 29 rides over contact 31at l30 contact 23 co operates with contact to complete the circuitagain, whereby the voltage between terminal 41 and common lead 43 is thesum of the outputs of switches 31 and 22; between 130 and 230 thevoltage is proportional to the shaft displacement; at 230 contact 29 isdisengaged from contact 310 and the voltage drops to zero until contactreaches contact 31e at 310; at 310 the circuit is again completedthrough winding 15 and 40 and the voltage is proportional to shaftdisplacement up to 360. This action keeps repeating as the displacementof shaft 13 increases. Although only six contacts have been shown onswitch 31 it is apparent that any number of contacts may be used toincrease the range of the computer.

In a similar manner the voltage between terminal of relay 42 and commonlead 43 is the sum of the voltages from switch 32 and terminals 2312 sothat the voltage of terminal 44 with respect to lead 43 plotted againstdisplacement of shaft 13 is as shown by the solid line in P16. 5:Between 0 and 40 the movable contact 30 cooperate with the dead contact32a so that there is zero voltage at terminal 44; at 40 movable contact30 engages contact 32b and completes the circuit so that the voltage atterminal 44- is proportional to the displacement of shaft 13 between 40and 140 displacement; at 140 movable contact 30 is disconnected fromcontact 3212 so that the voltage at terminal 44 drops to zero andremains at zero up to 220, i.e. until the contact 30 cooperates withcontact 32d; between 220 and 320 the voltage between terminal and lead43 is proportional to shaft displacement; at 320 the contact leavescontact 32:1 and the voltage drops to zero. This action keeps repeatingfor each revolution of shaft 13.

The movable contact 45 of relay 42 is actuated by the cam 46 on shaft 13for each displacement i.e. at the 225 and 315 position. Cam 4-6 operatesswitch 47 which causes deenergization or energization of relay winding4-8 by the power supply 49. The deencrgized relay winding 48 allowsspring 50 to urge the movable contact 45 downward (in PEG. 1) tocooperate with the spring contact 41' which is connected to terminal 41.An energized relay winding 40 draws the movable contact 45 intocooperation with the spring contact 44 which is connected to terminalRelay 42 is of the make-beforebreak type, where movable contact 45momentarily ceoperates with both spring contacts 44 and 41 during itsoperation from one position to the other.

The output of the relay switch 42 taken between contact 45 and thecommon lead is applied to terminals 1 2- and it will be seen that thisvoltage is an uninterrupted, highly accurate voltage proportional to thedisplacement of shaft or 13 (when the voltage at terminals 18 is unity).

Thus, between 0-45 of shaft 13 displacement relay winding 48 isdeenergized, relay contact 45 cooperates with spring 41 and the voltageat terminals 14 i the voltage output of rotor winding 15 represented bythe linear output shown in FIG. 4.

At 45 the contact 45 is urged upward by the energized relay winding 48,and during its upward travel cooperates with contact 44 before beingdisengaged from contact 41. It is seen that for about five degrees toeither side of 45 the voltage at terminals 41 and 44 (with respect tolead 43) are equal so that no damage will result by the momentary shortcircuit. This make-before-break transfer operation is necessary, on theother hand, to ensure a continuous uninterrupted voltage at terminals14- for successful operation of servo motors controlled thereby. From 45to 135 the voltage at terminals 14' increases proportionally as in thelinear portion of FIG. 5 (between 40 and At the 135 point, the movablecontact 4-5 is again urged downward as relay winding 48 is deenergizedto select the voltage between terminal 41 and common 43 as the output ofrelay 42.

As the displacement of shaft 13 increases, the relay 4-2 selects thevoltage from either terminal 41 or 44 as prescribed by cam 46 to produceat terminals 14' a voltage proportional to the displacement of shaft 13or 10.

It will be seen that the cams 19, 20 and 46 do not require extremeprecision in manufacture and adjustment since there is a ten degreeregion in which the transfer from one output to the other may be made,and since the reversal of potentiometer output takes place duringperiods when the movable contacts 29 and 30 are riding over deadcontacts.

We claim:

1. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, potentiometers connected to each of saidcircuits and means for driving said potentiometers and step switches inpredetermined relation.

2. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, potentiometers connected to each of saidcircuits and means for driving said potentiometers and step switches inpredetermined relation and reversing switches for changing the polarityof the output of said potentiometers.

3. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, potentiometers connected to each of saidcircuits and means for driving said potentiometers and step switches inpredetermined relation and reversing switches for changing the polarityof the output of said potentiometers and means controlled by saidpotentiometer driving means for actuating said reversing and selectorswitches.

4. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, an induction potentiometer connected to each ofsaid circuits and means for driving said induction potentiometers andstep switches in predetermined relation.

5. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, an induction potentiometer connected to each ofsaid circuits and means for driving said induction potentiometers andstep switches in predetermined relation and reversing means for changingthe polarity of output of said induction potentiometers.

6. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, a potentiometer connected to each of saidcircuits and means for driving said potentiometers and step switches inpredetermined relation and means controlled by said potentiometerdriving means for actuating said reversing and selector switches.

7. In a device of the character described, a pair of circuits having anoutput, switch means, and means for selecting either of said pair ofcircuits and operating said switch means to connect said circuit to saidoutput, a step switch in each circuit, means for driving said stepswitches simultaneously, an induction potentiometer connected to each ofsaid circuits and means for driving said induction potentiometers andstep switches in predetermined relation =and reversing means forchanging the polarity of output of said induction potentiometers andmeans controlled by said potentiometer driving means for actuating saidreversing and selector switches.

8. In a precision multiplier having electrical and mechanical inputs andan electrical output, a pair of circuits, switch means for connectingeither of said pair of circuits to said output, a step switch in eachcircuit, means for driving said step switches simultaneously,potentiometers connected to each circuit and means for driving saidpotentiometers and step switches in predetermined relation.

9. In a precision multiplier having electrical and mechanical inputs andan electrical output, a pair of circuits, switch means for connectingeither of said pair of circuits to said output, a step switch in eachcircuit, means for driving said step switches simultaneously,potentiometers connected to each circuit and means for driving saidpotentiometers and step switches in predetermined relation and means forchanging the polarity of output of said potentiometers.

10. In a precision multiplier having electrical and mechanical inputs.and an electrical output, a pair of circuits, switch means forconnecting either of said pair of circuits to said output, a step switchin each circuit, means for driving said step switches simultaneously,potentiometers connected to each circuit and means for driving saidpotentiometers and step switches in predetermined relation and means forchanging the polarity of output of said potentiometers and meanscontrolled by said potentiometer driving means for actuating saidreversing means and said selector switches.

11. An electrical apparatus, which comprises a series of terminals, oneof which is a reference terminal, means for maintaining a referencevoltage on the reference terminal and voltages of predetermined valuesrelative to the reference voltage on the respective other terminalsalong the series, and means for deriving voltages intermediate those onthe terminals, said means including a first inductive element connectedacross two of said terminals along said series, second and thirdinductive elements positioned in magnetic flux relation with said firstinductive element and in quadrature relation with each other, means forcontinuously varying the magnetic flux relation of said second and thirdinductive elements with respect to said first inductive element, atleast one of said second and third elements producing a linear potentialat all times, and means for alternately connecting said second and thirdinductive elements to successive terminals along the series.

12. An electrical apparatus, which comprises a series of terminals, oneof which is a reference terminal, means for maintaining a referencevoltage on the reference terminal and voltages of predetermined valuesrelative to the reference voltage on the respective other terminalsalong the series, and means for deriving voltages intermediate those onthe terminals, said means including a first inductive element connectedacross two of said terminals, second and third inductive elementspositioned in magnetic flux relation with said first inductive elementand in quadrature relation with each other, means for rotatably varyingthe magnetic flux relation of said second and third inductive elementswith respect to said first inductive element, and means operablyconnected with said last-named means for connecting said second andthird inductive elements to alternate terminals along said series, saidmeans being synchronized to effect said connections during therespective linear ranges of the potentials induced in said second andthird inductive elements.

13. An electrical apparatus, which comprises a series of terminals, oneof which is a reference terminal, means for maintaining a referencevoltage on the reference terminal and voltages of predetermined valuesrelative to the reference voltage on the respective other terminalsalong the series, and means for deriving voltages intermediate those onthe terminals, said means including a first inductive element connectedacross two of said terminals, second and third inductive elementspositioned in magnetic flux relation with said first inductive elementand in quadrature relation with each other, means for rotating saidsecond and third inductive elements whereby to vary their magnetic fluxlinkage with said first inductive element, and switch means responsiveto said rotation for alternately connecting said second and thirdinductive elements to sequential terminals along said series, saidswitch means being synchronized to effect said connections during therespective linear ranges of the potentials induced in said second andthird inductive elements.

14. An electrical apparatus, which comprises a series of terminals, oneof which is a reference terminal, means for maintaining a referencevoltage on the reference ter minal and voltages of predetermined valuesrelative to the reference voltage on the respective other terminalsalong the series, and means for deriving voltages intermediate those onthe terminals, said means including a first inductive element connectedacross two of said terminals, second and third inductive elementspositioned in magnetic flux relation with said first inductive elementand in quadrature relation with each other for inducing overlappinglinear potentials in said second and third inductive elements, means forconnecting said second and third inductive elements hand-over-hand tosuccessive terminals along said series, and means operably connectedwith said last-named means for varying the magnitude and phase of thepotentials induced in said second and third inductive elements so thatthe algebraic sum of the linear portion of the induced voltage and thetapped voltage in said second element is always equal to the algebraicsum of the linear portion of the induced voltage and the tapped voltagein said third element.

15. An electrical apparatus which comprises a series of terminals, oneof which is a reference terminal, means for maintaining a referencevoltage on the reference terminal and voltages of predetermined valuesrelative to the reference voltage on the respective other terminalsalong the series, and means for deriving voltages interq n o II1 dlalI6those on the terminals, said means including a first inductive elementconnected across two of said terminals, second and third inductiveelements serially connected and positioned in magnetic flux relationwith said first inductive element and in quadrature relation with eachother, means for connecting said second and third inductive elementshand-over-hand to successive terminals along said series, and meansoperably connected with said last-named means for varying the magnitudeand phase of the potentials induced in said second and third inductiveelements so that same total potential is developed across each saidelement from its common serial connection to a reference pointthroughout the common linear range of the induced potentials.

References Cited in the file of this patent UNITED STATES PATENTS2,625,327 Agins Jan. 13, 1953

